NUTRIENT COMPOSITION, QUALITY EVALUATION AND ACCEPTABILITY OF “GARI” FORTIFIED WITH TOASTED AFRICAN YAM BEAN SEED FLOUR
1.1 Background of study
The search for solution to malnutrition problem in its various forms particularly in developing countries necessitated the enhancement of nutritive quality of staple foods through improved processing, enrichment and fortification. “Gari” (toasted cassava meal) is one of such basic staples that demand attention considering its position in the dietary regime of a developing country like Nigeria (Okafor, 1992).
Gari is a fermented, dewatered and toasted starchy granule from cassava which is widely consumed all over West Africa and in Brazil where it is known as ‘farinha de manioca’ (Lancaster et al., 1982). Gari is one of the most popular forms in which cassava (Manihotesculenta Crantz) also known as manioc is consumed in Nigeria and some other parts of West Africa (Kordylas, 1990). It is a major component of everyday diet in Nigeria providing about 11.835kJ/person/day (Osho, 2003). Traditionally, it is produced by pressing the juice out of peeled, grated cassava roots and allowing a natural lactic acid fermentation to take place for 2-5 days. The fermented mash is then toasted in an open aluminum pan over open fire until the starch gelatinizes and the moisture content reduces to less than 12% dry basis (Chuzel et al., 1986). Cassava from which this important staple is produced is low in protein and deficient in essential amino acids. The crude protein content of locally produced gari vary between 1.03 % -2 % and the level of cyanide vary from 0 to 32mg HCN equivalent Kg-1 depending on the cassava variety and processing method (Oke, 1994; Ojo and Deane, 2002). Gari has been shown to be a rich source of energy but of poor protein source (1.03 %) compared to other food groups like grains (FAO, 1997). Gari has low levels of methionine, tryptophan, lysine and phenylalanine (Okigbo, 1980). High protein foods of animal origin such as meat, fish, milk and eggs are very expensive especially for the low income earners who are in the majority among the population of West African sub-region. Although efforts to increase the local production of these animal protein sources to make prices affordable are still ongoing (Akerele, 1967), fortification of gari with plant protein may be another alternative. There is therefore, need to search for cheaper but good quality protein sources that are readily available (Oluwamukomi, 2008). Gari is never eaten alone as a full meal but is rather taken with vegetable stew that can provide other nutrients like protein (Obadina et al., 2006). However, the exorbitant cost of animal protein for low income earners deters the inclusion of such animal protein source in the soup that gari is eaten with. This fact makes the need to improve the protein quality of gari imperative (Osho, 2003; Oluwamukomi et al., 2005). It is therefore, logical to source protein fortificants from plant sources like African yam bean, soybeans, cowpea and bambara nuts among others. African yam bean unlike other afore mentioned plant protein sources has not found uses in many food formulations as soybean hence it is said to be unexploited. African yam bean as one of the ideal plant protein sources for protein supplementation of starchy foods has been proposed because it will also help to extend the use of lesser known and underutilized legumes in a number of food preparations especially in the developing countries for human consumption (Nwokeke et al., 2013).
The African yam bean [Sphenostylis stenocarpa (Hochst. Ex A. Rich) Harms] is a climbing legume adapted to lowland tropical conditions. It is one of the lesser-known legumes (Apata and Ologhobo, 1990) and widely cultivated in the southern parts of Nigeria. Nigeria produced about 3,424 tonnes of African yam bean in 2010. Like most grain legumes cultivated in Africa, African Yam bean is rich in protein (19.5%), carbohydrates (62.6%), fat (2.5%), vitamins and minerals (Iwuoha and Eke, 1996). The protein is made up of over 32 % essential amino acids, with lysine and leucine being predominant (Onyenekwe et al., 2000). African yam bean is a cheaper protein source than animal products such as meat, fish, poultry and egg – therefore it is consumed worldwide as a major source of cheap protein especially in developing countries where consumption of animal protein may be limited as a result of economic, social, cultural or religious-factors (Olayide, 1982). This work therefore seeks to determine the extent to which AYBS (African yam bean Seeds) can improve the nutrient quality and acceptability of AYBS containing gari.
1.2 Statement of problem
Cassava tubers consist almost entirely of starch and are particularly low in protein (about 1-2 %), so dependence on cassava diets may lead to serious protein deficiency problems. Gari is never eaten alone most times as a full meal but is rather taken with vegetable stew/soup/sauce that can provide other nutrients like protein. However, the exorbitant cost of animal protein especially for low income earners deters the inclusion of such animal protein source in the stew that gari is eaten with. Improving the protein content of gari may be an alternative and affordable option. Fortification of cassava product like gari with plant protein is a viable affordable alternative to tackle specifically the problem of protein energy malnutrition in those areas affected by malnutrition. This plant protein can be sourced from unexploited indigenous legumes with high protein content (18.1 to 25.8 %) like African yam bean seeds